The subject matter disclosed herein relates generally to systems and methods for computed tomography (CT) imaging.
In CT imaging, an X-ray source may be rotated around an object of interest (e.g., a patient, organ of a patient) to obtain imaging information. During a clinical scan, X-rays emitted from the X-ray source, attenuated by the object of interest, may be collected or detected by a detector and used to reconstruct a medical image.
The object of interest is injected with a contrast agent (e.g., radiocontrast agent, an ionic contrast agent, a barium sulfate contrast agent, a blood agent) to provide maximum contrast in the imaging information. The clinical scan is preferably performed at locations of the object of interest when the contrast agent has filled the desired locations. For obtaining imaging information of the object of interest for long distances, such as greater than three hundred millimeters, the clinical scan ideally follows the contrast velocity rate of the contrast agent traversing within the object of interest. The contrast velocity rate is dependent on the blood flow rate of the object of interest, which may vary between different objects of interest and/or vary locally within the object of interest. If the clinical scan speed is too fast or too slow with respect to the contrast velocity rate, the scanner can “outrun” the contrast agent or the contrast agent may be depleted, respectively, leading to poor and/or uneven contrast opacification of the resultant image derived from the imaging information. To compensate, a larger contrast volume may be injected in subsequent scans leading to an unnecessary contrast dosage, which may be problematic for the patient.
Recently, to determine the contrast velocity rate, multiple bolus injections of the contrast agent are administered. During each injection, a continual scan is performed at separate locations, respectively, to determine a transit time of the contrast agent from an injection location to the respective location being scanned to determine an arrival time of the contrast agent. Based on the arrival times, a contrast velocity rate is approximated which is incorporated into a scan prescription. However, the multiple injections of the contrast agent and continual scans may be adverse to the health of the patient, such as increased radiation exposure, increased chance of having an adverse reaction to the contrast agent, and/or the like.
Thus, there is a need for ensuring a near-uniform contrast opacification of the resultant medical image without increasing risk to the patient.